JPH08168801A - Cold rolling mill for metallic sheet - Google Patents

Abstract

PURPOSE: To provide a cold rolling mill with which a material to be rolled excellent in cross-sectional shape and planar shape is rolled, whose resistance to accident such as breakage of a sheet at the time of rolling and durability of rolling rolls are excellent and with which a metallic sheet is manufactured by stable operation. CONSTITUTION: In the cold rolling mill which has roll groups consisting of work rolls 1, 1' and back-up rolls 2, 2' above and below and in which the metallic sheet is rolled by crossing the upper roll group and lower roll group in a horizontal plane, concave crowns 4 are imparted in the section within the contact width of the metallic sheet of the work rolls 1, 1' and/or backup rolls 2, 2'.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold rolling mill for metal sheets, and more particularly, it has excellent cross-sectional shape and flat shape of a material to be rolled, and has resistance to accident such as sheet breakage during rolling and rolling. The present invention relates to a cold rolling mill having excellent roll durability and capable of producing a metal sheet with stable operation.

[0002]

2. Description of the Related Art In recent years, customers have become more and more demanding regarding the properties of plate materials of various materials manufactured by rolling (hereinafter referred to as "rolled materials"), and high accuracy of plate thickness and plate shape is achieved. Is desired.

FIG. 2 shows the deformed shapes of the work roll and the metal plate during normal rolling. Generally, when the metal plate 3 is rolled, the work roll 1 is flatly deformed by the reaction force from the metal plate 3. Since the amount of deformation sharply decreases in the vicinity of the plate width end, a dimensional accuracy defect portion called edge drop occurs in which the plate thickness sharply decreases at the plate width end. This edge drop not only lowers the added value of the product, but also lowers the product characteristics itself in, for example, electromagnetic steel sheets. In addition, in order to give the plate thickness accuracy required as a product to the metal plate in which the edge drop has occurred, it is necessary to perform a process called trimming to cut off the plate end portion in the subsequent process, which lowers the production efficiency and the yield. Invited.

As a method of preventing the edge drop, for example, Japanese Patent Publication No. 60-51921 discloses that a pair of upper and lower work rolls are provided with a taper portion at one end thereof, and
A method has been proposed in which the work roll is movable in the axial direction, and the tape width end portion is brought into contact with the work roll for rolling to control the cross-sectional shape.

However, when performing continuous rolling in a cold tandem mill, the strip width of the rolled material changes variously depending on operating conditions. Therefore, when the edge drop is reduced by this method, the strip width changes. In addition, it is necessary to move the position of the taper portion of the work roll in the roll axial direction. However, when the work roll is moved under load, the control response is extremely slow, and the plate width change amount during operation is about 200 mm. Sometimes reaches dozens of seconds.

Therefore, in the vicinity of the joints of rolled materials having greatly different strip widths, a defective portion of strip thickness accuracy is generated over several tens of meters.

[0007] Further, "Crown / edge drop characteristics of cold cross rolling of thin plate" Proceedings of the 44th Joint Conference on Plastic Working, 308 (1993) p.149-152 and "Crown / edge drop characteristics in multi-pass rolling" Pp.25-28, Proceedings of the Spring 1994 Plastic Working Spring Lecture, pp.25-28 shows that upper and lower work rolls are used alone or in pairs with a backup roll to roll a metal sheet by intersecting in the horizontal plane. In the cross rolling method, the roll cross angle is set to be larger than usual and the rolled material is made to have a medium stretched shape, so that edge drop can be reduced. A method has been proposed in which the material to be rolled is an edge-up profile and ordinary rolling is performed after four stands to reduce the edge drop after the completion of all passes. In this method, the control response is relatively faster than that in the rolling using the work roll having the taper as described above, so that it is possible to reduce the defective portion when the running distance is changed.

FIG. 3 is a diagram showing the shape of a metal plate during normal rolling and the distribution of the rolling reaction force and the contact load between rolls. In this figure, the work roll and the backup roll under the metal plate are omitted. ing. In the strip rolling, the distribution of the rolling reaction force in the width direction changes depending on the rolling shape, and in the rolling having the seismic shape as shown in FIG. 3 (a), the rolling reaction force has a high distribution at the strip end, and as shown in FIG. 3 (b). It is generally known that in the rolling having the intermediate stretched shape shown, the central portion of the strip width has a high distribution.

Further, in the multi-stage rolling mill, the distribution of the contact load in the width direction also occurs between the work roll 1 and the backup roll 2, which corresponds to the distribution of the rolling reaction force between the metal plate 3 and the work roll 1. In the middle elongation rolling, the central part of the strip width has a high distribution. The contact load between the work roll 1 and the backup roll 2 has a great influence on the durability of the roll, and when the contact load becomes too high, cracks are generated on the roll surface during long-term use, Roll damage such as local chipping called spalling sometimes occurs.

On the other hand, even when roll cross rolling or taper work roll rolling is used, when the metal plate is made to have a medium elongation in order to reduce the above edge drop,
Since the elongation rate at the plate width end portion is smaller than that at the plate width center portion, a large tension is applied to the plate width end portion, and there is a problem that edge cracking or plate breakage sometimes occurs.

As described above, by applying roll cross rolling or taper work roll rolling, it is possible to improve the edge drop at the end of the metal plate, but it is necessary to carry out medium elongation rolling to prevent edge drop. Stretch rolling causes a large difference in the elongation in the rolling direction in the width direction, and excessive tension is generated, causing edge cracks and plate breakage at the plate edge, and increasing the contact load between rolls at the center of the plate width There is a problem such as damage.

As means for solving this problem, "reduction of cold-rolled edge drop by taper work roll"
As shown in CAMP-ISIJ Vol.5 Discussion 53 (1992) p.491-494, a method using tapered work rolls with a pair of convex taper rolls and an incurve is proposed, but a sufficient solution is proposed. Is hard to say.

[0013]

DISCLOSURE OF THE INVENTION In view of the above-mentioned prior art, the present invention is excellent in the sectional shape and flat shape of the material to be rolled, and in the resistance to accidents such as plate breakage during rolling and the durability of rolling rolls. It is also an object of the present invention to provide a cold rolling mill capable of producing a metal sheet with stable and stable operation.

[0014]

DISCLOSURE OF THE INVENTION The present inventors have focused on roll cross rolling which can reduce the edge drop of a metal plate by increasing the roll cross angle mentioned in the above-mentioned prior art, and have problems in roll cross rolling. The occurrence of medium stretch,
As a result of examining the means for eliminating the increase in the contact load between the work roll and the backup roll in the width center part and the generation of excessive tension at the plate edge part due to the difference in the elongation in the rolling direction in the width direction, The present invention has been completed.

The present invention relates to a cold rolling machine which has a roll group consisting of a work roll and a backup roll on the upper and lower sides, and rolls a metal plate by crossing the upper roll group and the lower roll group in a horizontal plane. And / or a cold rolling mill for a metal plate in which a concave crown is provided in a section within the contact width of the metal plate of the backup roll.

[0016]

The function of the present invention will be described below.

First, the reason why the edge drop of the rolled plate can be reduced in roll cross rolling will be described.

FIG. 4 shows (a) roll gap distribution when no load is applied, when a roll cross rolling is carried out using a normal work roll, and the work is cut along a plane perpendicular to the rolling direction.
FIG. 6B is an enlarged view of the deformed shape of the work roll surface under no load and under load, and a diagram showing the widthwise rolling reaction force distribution under load.

Upper and lower work rolls 1 and 1'and backup rolls 2 and 2'constitute an upper and lower roll group.
By crossing the upper and lower roll groups in the horizontal plane,
In the unloaded state, the roll gap in the width direction is schematically shown in FIG.
As shown in “Rolling characteristics of pair / cross rolling mill” Plasticity and processing, 28-321 (1987), 1067, it has the distribution shown in (a) and the following formula (1) is used according to the set roll cross angle. It is expressed by a quadratic equation given by

Cw = {2z ² tan ² θ / Dw} × 10 ³ (1) where Cw: roll gap distribution (μm), z: distance from roll width center (mm), θ: roll cross angle (Every time),
And Dw: Work roll diameter (mm).

When the metal plate 3 is rolled with a gap distribution as shown in FIG. 4 (a) when no load is applied, the amount of reduction is large at the center of the plate, while the amount of reduction is small at the end of the plate, so the width direction is reduced. There is a difference in the elongation in the rolling direction, and the tension at the edge of the plate increases, so that the rolled plate undergoes intermediate elongation. At this time, the rolling reaction force generated on the work rolls 1 and 1'has a distribution in which the width center portion becomes higher as in the case shown in FIG. 3 (b).

Further, the deformed shape of the roll also changes depending on the distribution of the rolling reaction force in the width direction, the roll undergoes greater deformation at the central portion of the strip width where the rolling reaction force is high, and at the plate end where the reaction force is small, Since the amount of deformation is small, as shown in FIG. 4B, there is no load (work roll surface before deformation).
With the convex roll surface shape, when the load (work roll surface after deformation) works to cancel the difference in the amount of reduction that occurs in the width direction, the effect is commonly called the "tension feedback effect" At the center of the width, the gap distribution is almost constant in the width direction.

Further, the rolled plate is also deformed in the width direction so as to cancel the difference in elongation in the rolling direction caused by the distribution of the roll gap, the width contraction occurs at the plate end, and the reduction amount near the plate end is small. , The "feedback effect of tension" is alleviated, and the effect of the initial roll gap distribution remains after rolling.

As a result, in accordance with the shape of the deformed work roll surface shown in FIG. 4 (b), the width center part has a substantially constant plate thickness due to the "tension feedback effect", and only the plate end part has the same thickness. The plate thickness distribution has no effect and has an edge up.

This phenomenon is caused by the geometrical gap formed between the upper and lower rolls even when the roll cross angle is changed by the formula (1) or when the work roll is provided with a conventional convex crown. Depending on the distribution, the difference in elongation in the rolling direction in the width direction changes, and the above-mentioned "tension feedback effect"
By changing the distribution of the rolling reaction force, the roll gap distribution during rolling has a shape corresponding to the roll cross angle and roll crown at the plate edge while maintaining a substantially constant distribution at the center of the plate width. .

Therefore, in roll cross rolling, (1)
It is possible to cause edge-up only at the plate edge by applying the secondary gap distribution shown in the formula and rolling. By increasing the roll cross angle, the width center maintains a constant plate thickness. At the same time, the edge-up amount can be increased.

By the way, the work rolls 1, 1'and the backup rolls 2, 2'are subject to bending deformation and contact deformation due to the rolling reaction force and the contact load between the rolls, respectively.
The amount of deflection differs depending on the difference in diameter of 2'and the difference in load distribution, work rolls 1 and 1'become more bent, and the contact deformation between the work roll and the backup roll also increases at the width center part. The contact load distribution is also high in the width center part.

Further, as the roll cross angle is increased, the difference in elongation in the rolling direction between the central portion of the strip width and the strip end portion becomes large, excessive tension is generated at the strip end portion, and the rolling reaction force at the strip width central portion is increased. Be too large. As a result, work roll 1,
The contact deformation between the 1'and the backup rolls 2 and 2'becomes larger in the plate central part, so that the contact load becomes excessive in the width central part.

Therefore, by applying roll cross rolling, edge drop can be prevented, but with flatness failure due to middle elongation, roll damage such as chipping and spalling of roll due to increase in contact load between rolls, and plate rolling. There is a problem that the edge of the rolled material is cracked or the plate is broken due to excessive tension at the ends.

In order to solve the above-mentioned problems, the difference in the amount of reduction between the width center portion and the plate end portion caused by the roll gap distribution is reduced, and the contact between the work roll and the backup roll at the width center portion is reduced. It is necessary to reduce the amount of deformation.

FIG. 1 is a front view showing an example of the shapes of work rolls and backup rolls used in the cold rolling mill of the present invention. In this example, the work rolls 1 and 1 ′ have a shape in which a concave crown 4 is provided at the center of the width, and the region of the concave crown 4 is limited to a range narrower than the plate width of the rolled plate.

FIG. 5 shows (a) roll gap distribution when no load is applied, when a roll cross rolling is carried out using the work roll of the present invention and the work is cut in a plane perpendicular to the rolling direction.
FIG. 6B is an enlarged view of the deformed shape of the work roll surface under no load and under load, and a diagram showing the widthwise rolling reaction force distribution under load.

When the work rolls 1 and 1'and the backup rolls 2 and 2'are paired as upper and lower roll groups and the upper and lower roll groups are crossed in a horizontal plane without load, a geometrical roll gap is obtained. As shown in FIG. 5 (a), the distribution of the concave crown 4 on the surface contacting the rolled plate is offset by the convex gap distribution generated by the roll cloth, resulting in a shape close to a flat shape. At the position corresponding to the plate end portion where no mark is given, the gap distribution is similar to that of the normal work rolls 1 and 1'of FIG. Also, work rolls 1, 1'and backup rolls 2,
On the surface in contact with 2 ', the portion provided with the concave crown is a gap.

When a metal plate is rolled with a gap distribution as shown in FIG. 5 (a) when no load is applied, it can be seen from the work roll surface position before and after deformation in FIG. The difference in the amount of reduction at the plate end is smaller than that in the case where a normal work roll is used, and the difference in the elongation in the rolling direction in the width direction is also small. Further, since the tension at the plate end is also reduced, it is possible to prevent the medium elongation of the rolled plate. The rolling reaction force generated on the work rolls at this time is such that the difference between the central portion and the plate end portion decreases as shown in FIG. 5 (b), and compared with the case of using the normal work rolls of FIG. 4 (b), It is possible to prevent an excessive rolling reaction force at the center of the width.

Further, the amount of contact deformation between the work rolls 1 and 1'and the backup rolls 2 and 2'is also reduced by the effect of the gap in the central portion, and the contact load between the rolls is also reduced.

On the other hand, at the plate end, a normal work roll 1,
Similar to the case of using 1 ′, it is possible to cause edge-up by the effect of providing the roll gap by the roll cloth.

That is, the edge-up generation effect of the plate end portion when the roll cross rolling is performed using the normal work rolls is utilized, and the rolling reaction force becomes excessively large when the normal work rolls are used. The concave crown is provided only in the central portion to reduce the rolling reaction force, improve the flatness of the rolled plate, and prevent the plate from breaking and the roll from breaking. Here, the reason for limiting the region of the concave crown to a range narrower than the plate width of the rolled plate is that when a concave crown is provided in a range of the plate width of the rolled plate or more, a roll cloth is used using a normal work roll. The convex roll gap distribution obtained when rolling is offset by the concave crown, and the roll surface in contact with the entire plate width including the plate end becomes a shape close to flat, and the amount of reduction at the plate end is Since it becomes large, edge drop occurs. On the other hand, if the range to which the crown is applied is too narrow with respect to the strip width, the reduction of the rolling reaction force at the center of the width becomes insufficient and the effect of reducing the rolling reaction force due to the provision of the concave crown cannot be obtained, resulting in poor flatness due to medium elongation. Or plate breakage may occur.

Therefore, the width for giving the concave crown is set to a range narrower than the plate width of the rolled plate, but it is preferable that the concave crown having a width of 1/2 or more of the plate width and 100 mm or more narrower than the plate width is formed on the roll. It is preferably provided.

Regarding the shape and size of the concave crown to be given, various combinations are conceivable, and a quadratic curve,
It can be given in various curve shapes such as a cubic curve and a sine curve, but it is desirable that it is close to the shape of the roll gap distribution generated by the roll cloth, and the contact load between the work roll and the backup roll is locally To prevent the increase, it is better to make the curvature as large as possible.

FIG. 6 shows an enlarged example of the shape of the work roll crown of the present invention. First, from the strip width of the rolled material to the width of the concave crown (L ₀ × 2), and an appropriate value in roll cross rolling. A predetermined amount Cw ₀ of concave crown at the center of the roll obtained from the formula (1) from the roll cross angle etc. is determined, and the following (2)
The entire roll shape may be determined by approximation with the equation (3).

Cw = Cw ₀ {1 + cos (πz / L ₀ )} (z ≦ L ₀ ) (2) Cw = 0 (z> L ₀ ) (3) where Cw: roll gap distribution (μm), z : Distance from central roll width (mm), Cw ₀ : amount of crown at concave crown center (μm), L ₀ : distance from center of region to which concave crown is applied (mm), and π: circumference ratio Is.

Further, FIG. 7 shows (a) roll gap distribution under no load when roll cross rolling is carried out using a backup roll having a concave crown, and cut at a plane perpendicular to the rolling direction, FIG. 6B is an enlarged view of the deformed shape of the work roll surface under no load and under load, and a diagram showing the widthwise rolling reaction force distribution under load.

When a concave crown 4 is provided on the backup rolls 2 and 2'and the metal plate 3 is rolled with a gap distribution as shown in FIG. 4 (a) is the same as the case of using the normal rolls, except that the work rolls 1 and 1'and the backup roll 2,
The work rolls 1 and 1'deform during rolling because there is a gap due to the concave crown 4 between 2 ', but contact occurs due to the effect of the gap in the central portion between the work rolls 1 and 1'and the backup rolls 2 and 2'. The amount of deformation is reduced, and the contact load at the center is reduced. Further, since the work rolls 1 and 1'bend along the shape of the concave crowns of the backup rolls 2 and 2 ', the reduction amount of the plate central portion and the plate end portion is when the normal backup rolls 2 and 2'are used. Smaller than
The elongation in the rolling direction in the width direction is also small. Further, since the tension at the edge of the plate is also reduced, it is possible to prevent intermediate elongation of the rolled plate. As for the rolling reaction force generated on the work rolls 1 and 1 ′ at this time, as shown in FIG. 7B, the difference between the central portion and the plate end portion is reduced, and the work roll is provided with a concave crown.
Since the result is similar to that of (b), it is possible to prevent an excessive rolling reaction force at the width center portion.

From the above, the effect of the present invention can be obtained not only when the work roll but also when the backup roll is provided with the same concave crown. Further, it goes without saying that the same effect can be obtained by providing the concave crown to both the work roll and the backup roll.

[0045]

EXAMPLES The effects of the present invention will be described below based on examples.

(Example 1) Roll cross rolling of a metal plate was carried out using a work roll provided with a concave crown as shown in FIG. Work roll diameter: 550mmφ, backup roll diameter: 1500mmφ, roll body length: 1800mm 4
Using Hi's pair cross rolling machine, plate thickness 2.0mm, width 1200mm
The metal plate made of the ordinary steel of was rolled at a reduction rate of 30%. The upper and lower work rolls are provided with a concave crown represented by the formula (2). The concave crown shape is L ₀ = 400 mm, Cw ₀ = 30 μm.
m. The roll cross angle θ was set to 1.0 °. As the rolling oil, a mineral oil rolling oil having a viscosity of 40 cSt at 40 ° C. was used in an emulsion, and rolling was performed at a rolling speed of 450 m / min.

As a comparative material, a normal work roll not provided with a concave crown was used, and the roll cross angle was 1.0.
Rolling was also carried out under the conditions set to 0 ° and 0.3 °.

FIG. 8 shows the plate thickness deviation of the rolled material in the plate width direction, and FIG. 9 shows the steepness at the position of the rolled material in the plate width direction. FIG.
From, the cross-sectional shape in the width direction of the metal plate after rolling,
The planar shape can be seen from FIG. The plate thickness deviation is a plate thickness deviation in the plate width direction with reference to the plate central portion of the rolled material. The steepness is calculated by converting the difference in elongation in the rolling direction between each position in the strip width direction and the central part of the strip. When the steepness is negative, the elongation is small compared to the central part of the strip (so-called medium stretch state). The positive steepness means a state in which the elongation is larger than the central portion of the plate (so-called ear wave state).

From FIG. 8 and FIG. 9, the steepness is almost 0 and a flat shape is obtained under the condition of rolling with a roll cross angle of 0.3 ° using a normal work roll (Δ in the figure). However, as for the plate thickness deviation, a large edge drop occurs at the plate end. On the other hand, the conditions under which a normal work roll was used to roll at a roll cross angle of 1.0 ° (□ in the figure)
As for the plate thickness deviation, the plate has a rectangular cross section even at the plate edge and is slightly edged up, but the steepness is -2% or more, which is a large intermediate stretch shape, and excessive tension is applied to the plate edge. You can see that it is occurring.

In contrast to these comparative examples, in the example of the present invention (◯ in the figure), the plate thickness deviation keeps a rectangular cross section, and the effect of roll cloth appears as in the case of using the conventional work roll. . On the other hand, the steepness is -1% or less, and although the shape is slightly medium, it is understood that the difference in elongation strain is remarkably reduced as compared with the conventional example, and the tensile force generated at the plate end portion is reduced.

(Embodiment 2) Next, with respect to the present invention example, the influence of the concave crown amount of the roll and the roll cross angle was investigated. Using the same rolling mill and rolling plate as in Example 1, the edge drop amount and the steepness were measured when the roll cross angle θ and the concave crown amount Cw ₀ in the equation (2) were variously changed. A rolling oil was 30%, and a rolling oil was a mineral oil rolling oil having a viscosity of 40 cSt at 40 ° C., which was used as an emulsion, and rolling was performed at a rolling speed of 450 m / min.

FIG. 10 shows the relationship between the roll cross angle and the edge drop amount of the rolled material, and FIG. 11 shows the relationship between the roll cross angle and the steepness. The edge drop amount was evaluated by the difference in plate thickness between the positions 75 mm and 15 mm from the plate edge, E _75-15 , and the steepness was evaluated by the steepness λ ₁₅ at the position 15 mm from the plate end. Further, in the symbols in the figure, ◯ is a roll having a concave crown of Cw ₀ = 60 μm, □ is a roll having a concave crown of Cw ₀ = 30 μm, and Δ is a normal roll having no concave crown. This is the result of rolling.

From FIG. 10, the edge drop amount E
_75-15 decreased with the roll cross angle regardless of the size of the concave crown provided at the center of the width of the roll. Therefore, it is understood that the concave crown in the present invention has a small influence on the plate profile near the edge, and the roll cross rolling can reduce the edge drop.

On the other hand, as shown in FIG. 11, the steepness of the rolled metal sheet changes from an ear wave to an intermediate elongation tendency as the roll cross angle increases, but it depends on the size of the concave crown in the present invention. It can be seen that as the concave crown becomes larger, the steepness tends to be an ear wave (the middle stretched shape is relaxed), and the flatness of the metal plate is improved by providing the concave crown of the present invention.

Example 3 Next, the influence of the plate width and plate thickness of the metal plate of the present invention was investigated. The same rolling mill and rolling plate as in Example 1 were used, and various thickness and width tests were carried out. At this time, the roll cross angle was set such that the steepness of the shape of the rolled metal plate was a constant value (steepness λ ₁₅ = -1%).

The shape of the concave crown provided in the central portion of the width of the upper and lower work rolls is expressed by the formula (2), L ₀ = 300 mm, C
w ₀ = 30 μm. Here, a rolling reduction oil was 30%, and a rolling oil was a mineral oil rolling oil having a viscosity of 40 cSt at 40 ° C., which was used in an emulsion, and rolling was performed at a rolling speed of 450 m / min.

FIG. 12 shows the relationship between the edge drop improvement amounts when the width and thickness of the base material of the metal plate are changed. The edge drop improvement amount is the edge drop amount E in the conventional example (roll cloth rolling using a normal work roll).
Edge drop amount in the present invention embodiment for _75-15 E _75-15
Was evaluated (the difference between the edge drop amount of the conventional example and the edge drop amount of the present invention example).

From these results, there is an effective range for the relationship between the plate width of the metal plate and the width of the concave crown applied to the work roll, and when the plate width is about the same as the width of the concave crown (the plate width is 6
(Corresponding to 00 mm), the effect of improving the edge drop according to the present invention is small. This is because the convex roll gap distribution formed by the roll cloth is offset by the concave crown,
This is because the effect of the crown at the plate edge is canceled.

On the other hand, when the plate width is too large with respect to the width of the concave crown applied to the work roll, that is, when the plate width is 1400 mm (corresponding to about 2.3 times the crown applied width) or more, The effect of improving edge drop is reduced. This is because the flatness is more likely to collapse as the plate width is wider, and the effect of relaxing the middle stretched shape by the recessed crown provided is small, and there is not much difference from normal rolling.

Therefore, as described above in the operation, the width for giving the concave crown is set to a range narrower than the plate width of the rolled plate, but it is preferably 1/2 or more of the plate width and 100% of the plate width.
It is preferable to provide the roll with a concave crown having a width narrower than mm.

However, even in these cases, the amount of edge drop reduction for the same shape is about the same as that of the conventional method, and the method of the present invention can operate even if the plate width and the width of the concave crown region are not in an appropriate relationship. Normal operation is possible without any hindrance.

On the other hand, the influence of the base metal plate thickness of the metal plate is that the larger the plate thickness, the greater the edge drop improvement amount, and the wider the effective range of the plate width of the metal plate with respect to the width of the concave crown.

In the actual operation in the production line, since the plate width, the plate thickness and the material of the metal plate to be supplied are various, in the same concave crown shape, the method of the present invention can be applied to all sizes and materials. Although it is difficult to sufficiently exert the effect, for example, the control characteristic as shown in FIG. 12 is held as a table, and the most average size, or particularly, according to the production schedule every time the work rolls are replaced. An appropriate concave crown shape may be set for those for which it is necessary to manage the edge drop small.

(Embodiment 4) A backup roll having a concave crown as shown in FIG. 7 was used, and the work roll was not provided with a concave crown. The metal sheet was used for roll cross rolling. The upper and lower backup rolls were provided with a concave crown represented by the formula (2), and the concave crown shape was L ₀ = 400 mm and Cw ₀ = 30 μm as in Example 1. The roll cross angle θ was set to 1.0 °. In addition, as rolling oil
A mineral oil-based rolling oil having a viscosity of 40 cSt at 40 ° C. was used in an emulsion, and rolling was performed at a rolling speed of 450 m / min and a reduction rate of 30%.

As a comparative material, an ordinary backup roll not provided with a concave crown was used, and the roll cross angle was
Rolling was also performed under the conditions set to 1.0 ° and 0.3 °.

FIG. 13 shows the plate thickness deviation of the rolled material in the plate width direction,
FIG. 14 shows the steepness of the rolled material in the plate width direction.

13 and 14, the steepness is almost 0 and a flat shape is obtained under the condition that rolling is performed at a roll cross angle of 0.3 ° using a normal backup roll (Δ in the figure). However, as for the plate thickness deviation, a large edge drop occurs at the plate end. On the other hand, under the conditions of rolling using a normal backup roll at a roll cross angle of 1.0 ° (□ in the figure), the plate thickness deviation keeps a nearly rectangular cross section even at the plate edge, and slightly increases the edge. However, the steepness is as large as −2% or more in the middle stretched shape, and it can be seen that excessive tension is generated at the plate edge.

In contrast to these comparative examples, when the backup roll provided with the concave crown of the present invention example (○ in the figure) was used, the plate thickness deviation kept a rectangular cross section, and the conventional backup roll was used. As in the case, the effect of roll crossing appears. On the other hand, the steepness is about -1%, and although the shape is slightly elongated, it can be seen that the difference in elongation strain is remarkably reduced as compared with the conventional example, and the tensile force generated at the plate end portion is reduced.

Compared with Example 1 in which the work roll was provided with a concave crown, in this example in which the backup roll was provided with a concave crown, the edge drop improving effect was large, but the intermediate stretched shape was slightly large and the normal roll cloth was used. The shape is similar to rolling. This is because the effect of the concave crown imparted to the backup roll is reduced by the contact deformation between the work roll and the backup roll. Therefore, when the concave crown is provided only to the backup roll, the concave crown amount Cw ₀ may be set to be larger than when the concave crown is provided to the work roll.

Example 5 Next, the effect of the present invention was investigated in actual operation.

In a 5-stand cold tandem rolling line consisting of rolling mill groups similar to those in Example 1, the edge drop amount at the exit side of the final stand when roll cross rolling was performed at 1 to 3 stands and the plate The rate of breakage and the rate of roll accidents were investigated.

The roll dimensions provided in all the rolling mills of the stands are the same as in Example 1, and the upper and lower work rolls of the first to third stands are provided with concave crowns represented by the formula (2), The crown shape was L ₀ = 400 mm and Cw ₀ = 30 μm. Further, roll cross rolling was performed with 1 to 3 stands.

Thickness is 6.0 to 2.0 mm, width is 800 to 1500 mm
Rolling was performed using the metal plate of No. 3 to obtain a finished thickness of 2.5 to 0.35 mm. In addition, the roll cross angle etc. is set from the actual value of the operation data by the edge drop amount E at the exit side of the final stand.
_It was set _so that _75-15 was below the target value of 20 μm.

On the other hand, using an ordinary work roll, the shape of the rolled plate on the stand-out side is flat (the steepness is ± 1.0%).
Examples comparing the case where the rolling by setting the roll cross angle of 1-3 stands to be within) 1, if reducing the edge drop (edge drop amount E _{75- 15} makes a rolling so as to 20μm or less) is Was used as Comparative Example 2 and the same investigation was conducted. The shape was detected online by a shape meter installed between the stands, and the roll cross angle between the stands was feedback-controlled based on the value.

FIG. 15 shows the actual value of the edge drop amount, FIG. 16 shows the plate breakage occurrence rate, and FIG. 17 shows the actual value of the roll accident occurrence rate. The edge drop amount is E _75-15
Is the value of.

In Comparative Example 1 in which the shape is flattened by using a normal roll, it can be seen that a large edge drop occurs in the final product and the variation is large.

Further, in the case of the comparative example 2 in which the roll cross angle control is performed so as to reduce the edge drop by using the normal work roll, the edge drop amount is the target value.
Although it is reduced to 20 μm or less, both the plate breakage occurrence rate and the roll accident occurrence rate are increased 5 to 6 times that of Comparative Example 1.

On the other hand, in the present invention example, the edge drop amount is almost the same as that of the comparative example 2, and
The plate breakage occurrence rate and the roll accident occurrence rate are good results that are not different from the actual results of Comparative Example 1. Here, the reason why the variation of the edge drop amount is larger than the target value is that the size of the concave crown and the size of the rolled plate are not appropriate.

Therefore, according to the present invention, the edge drop of the metal plate can be significantly reduced as compared with the conventional rolling method, and the shape after rolling is slightly medium stretched, but this is a problem in operation. It is possible to reduce to a non-existent range, and it is possible to suppress the generation of excessive tension or roll-to-roll contact load that causes a roll accident due to plate breakage, roll surface cracks, spalling, or the like.

[0080]

According to the present invention, a metal plate having a small edge drop can be manufactured without causing a large shape defect. Furthermore, since the magnitude of the tension acting in the rolling direction of the metal plate is also made uniform in the width direction, cracks and fractures do not occur in the rolled plate, and since it is possible to suppress the occurrence of excessive roll-to-roll contact load, It is possible to prevent accidents such as cracks and chips.

[Brief description of drawings]

FIG. 1 is a front view showing an example of the shapes of a work roll and a backup roll used in a cold rolling mill of the present invention.

FIG. 2 is a diagram showing deformed shapes of a work roll and a metal plate during normal rolling.

FIG. 3 is a diagram showing a shape of a metal plate during normal rolling and distribution of rolling reaction force and contact load between rolls, (a) conditions for selvedge rolling, and (b) conditions for medium elongation rolling. Indicates.

FIG. 4 shows (a) roll gap distribution when no load is applied, and (b) shows when a roll cross rolling is performed using a normal work roll, when cut along a plane perpendicular to the rolling direction. FIG. 4 is an enlarged view of a deformed shape of the work roll surface under load and under load, and a view showing a width direction rolling reaction force distribution under load.

FIG. 5 shows (a) roll gap distribution when no load is applied, and (b) when roll cross rolling is performed using the work roll of the present invention, when cut along a plane perpendicular to the rolling direction. FIG. 4 is an enlarged view of a deformed shape of the work roll surface under no load and under load, and a diagram showing a width direction rolling reaction force distribution under load.

FIG. 6 is a diagram showing an example of the shape of the work roll crown of the present invention.

FIG. 7A is a roll gap distribution when no load is applied when roll cross rolling is performed using the backup roll of the present invention, and is cut in a plane perpendicular to the rolling direction;
FIG. 4 is an enlarged view of the deformed shape of the work roll surface under no load and under load, and a view showing the widthwise rolling reaction force distribution under load.

FIG. 8 is a diagram showing a plate thickness deviation of a rolled material in a plate width direction.

FIG. 9 is a diagram showing steepness of a rolled material at a position in the plate width direction.

FIG. 10 is a diagram showing a relationship between a roll cross angle and an edge drop amount of a rolled material.

FIG. 11 is a diagram showing a relationship between a roll cross angle and a steepness of a rolled material.

FIG. 12 is a diagram showing a relationship between edge drop improvement amounts when a plate width and a plate thickness of a base material of a metal plate are changed.

FIG. 13 is a diagram showing a plate thickness deviation of a rolled material in the plate width direction.

FIG. 14 is a diagram showing steepness of a rolled material at a position in the plate width direction.

FIG. 15 is a diagram showing actual values of the edge drop amount in actual operation.

FIG. 16 is a diagram showing an actual value of a plate breakage occurrence rate in an actual operation.

FIG. 17 is a diagram showing actual values of roll accident occurrence rates in actual operation.

[Explanation of symbols]

 1, 1 ': Work roll 2, 2': Backup roll 3: Metal plate 4: Concave crown

Claims (1)

[Claims] 1. A cold rolling mill which has a roll group consisting of a work roll and a backup roll at the top and bottom, and rolls a metal plate by crossing an upper roll group and a lower roll group in a horizontal plane, Alternatively, a cold rolling mill for a metal plate, wherein a concave crown is provided in a section within a contact width of the metal plate of the backup roll.